ARRANGEMENT IN CONNECTION WITH A WEAR RESISTANT COATING IN PARTICLE FEEDER AND METHOD FOR PRODUCING THE SAME

Abstract: A rotating gate feeder (1) for feeding substantially particulate material comprises a housing (2) and a rotor (3) and also an end cap (8) at each end of the housing. The invention is characterised in that a wear-resistant coating (6) is cast directly onto the inner wall (14) of the housing which faces towards the rotor (3). The inner wall (14) of the housing functions as an outer mould and a purpose-adapted core (15) is used as an inner mould. The housing (2) may be provided at certain points with release zones on the surfaces (14) which face towards the cast wear-resistant coating (6). One or more wear members (12) having greater wear resistance than the moulding compound may be embedded therein.

Description: AR R AN GE MEN T I N CONNECTION WITH A WEAR RESIGTANT COATING I N P A R T I CL E FEEDER AND METHOD FOR PRODUCING THE SAME The invention relates to a wear-resistant coating arrangement in a rotating gate feeder for the feeding of substantially particulate material. The gate feeder comprises a housing and a rotor and also an end cap at each end of the housing. In such gate feeders, or star feeders as they are also called, great wear occurs on the interior surface of the housing when the particulate material comes into contact with and scrapes along the interior surface of the housing. The greatest wear occurs when abrasive material is fed through the feeder whilst it operates at great air pressure differences, which causes "sandblasting" between the rotor blades and the housing. It is therefore common to equip the interior wall of the housing with a wear-resistant coating. This wear-resistant coating may be applied in thin layers of hard chrome, silicon carbide, tungsten carbide or similar, or may consist of a detachable lining of a wear-resistant material which is placed so as to fit closely against the interior wall of the housing. Detachable liners of this kind are known from GB Patent No. 1 182 992 and GB Patent No. 1 161 204. These detachable wear- resistant linings have the advantage that they can easily be replaced when they are worn out, but they have the disadvantage of having to be manufactured with great precision so as to fit inside the housing. They must therefore be manufactured in steel or another material which can readily be processed, and which thus does not have the same high degree of wear resistance. The requirement of precision means that these linings will also be expensive to manufacture. Moreover, the linings must be attached and locked into place with great care. If the lining does not fit with precision inside the housing, it may move relative to the housing whilst the feeder is in operation, thereby increasing the wear rate considerably and the lining may break and cause damage to both the rotor and the housing. To achieve greater wear resistance and to overcome the said disadvantages, by means of the present invention, a wear- resistant coating is provided which is cast directly on to the inner wall of the housing which faces towards the rotor, the housing inner wall functioning as an outer mould and with a purpose-adapted core as the inner mould. The wear-resistant coating consists of a large proportion of granular and extremely hard particles which are held together by a castable binder. In this way, a highly wear-resistant surface is obtained which at the same time is rough and provides great through-flow resistance to air containing abrasive particles. In addition to great wear resistance, this solution therefore also provides reduced air leakage through the gap between the surface and the wings of the rotor. This results in reduced wear on the rotor wings. By producing the wear-resistant coating in this way, a wear- resistant coating is obtained that is adapted with precision to the interior wall of the housing whilst the wear-resistant surface is adapted to the diameter of the rotor. The wear- resistant coating adheres with great strength to the interior wall of the housing and will not be able to fall out even when subjected to great mechanical stress. To facilitate the removal of the the wear-resistant coating when it needs to be replaced, a release coating may be applied at certain points on the interior wall of the housing, prior to the wear-resistant coating being cast in place. The release coating weakens the adhesion to the interior wall of the housing. This means that when tools are used, such as a hammer and chisel or similar, the wear-resistant coating will become loosened in certain zones and be released on being broken into pieces . The invention also relates to a method for providing a wear- resistant coating of this kind in that the wear-resistant coating is cast directly on to the interior wall of the housing which faces towards the rotor, with the housing functioning as an outer mould and with a purpose-adapted core functioning as an inner mould. The invention will be explained in more detail below with reference to the attached figures where: Figure 1 illustrates the housing with a wear-resistant coating cast in place and the rotor mounted in place. Figure 2 is a lateral view of the gate feeder and with wear- resistant coating applied to the end caps. Figure 3 illustrates the same as Figure 1, but in this case wear members are embedded in the wear-resistant coating. Figure 4 is a lateral view of the gate feeder illustrated in Figure 3, where embedded wear members are also found on the end caps. Figure 5 shows the housing whilst the wear-resistant coating is being cast with the core in place. Figure 1 illustrates a gate feeder 1 comprising a housing 2 and a rotor 3. Particulate material is fed in through an inlet opening 4 and fed out with the aid of the rotor 3 through outlet opening 5. A wear-resistant coating 6 is disposed on the internal wall 14 of the housing which faces the rotor 3. The housing is equipped with a hole 7 through which the moulding compound which forms the wear-resistant coating is poured. Figure 2 illustrates end caps 8 which have a wear-resistant coating 9 cast on to the internal surface thereof . In the end caps there are also provided bearings 10 on which the rotor is mounted and seals 11 which seal against the housing 2. To further enhance the wear-resistant properties of the wear- resistant coating or for use which requires other properties, in the embodiment illustrated in Figure 3, wear members 12 are embedded in the moulding compound. These may be in a homogenous (compact) version of the granular material in the moulding compound or other materials of great wear resistance. The end caps 8 may similarly be equipped with such wear members 13. The interior wall 14 of the housing which faces towards the rotor 3 forms the outer mould for casting the wear-resistant coating 6. As an inner mould an especially purpose-adapted core 15 is used. This has the same diameter as the largest diameter of the rotor. The surface 19 is very smooth so that the surface 18 of the wear-resistant coating will be a even as possible. The core 15 may be in one piece, or may consist of two portions 15a and 15b as shown in Figure 5. This makes the insertion and withdrawal of the core after moulding easier. The core portions are held in place in that non- illustrated press means are disposed between the core portions and press these apart from one another against the contact surfaces 16 and 17 on either side of the housing. Prior to casting the coating, a release coating may be applied to certain zones of the inner wall 14 of the housing 2. The proportion of such release coating in relation to the part of the inner wall of the housing to which no release coating is applied, may be varied according to how well one would like the wear- resistant coating to adhere to the inner wall of the housing. Different types of release coating may also be selected with regard to the adhesive properties thereof. In order to embed wear members 12 in the surface of the moulding compound which faces the rotor, wear members may be glued or attached in some other way on to the core prior to the insertion of the core into the housing. During the casting of the wear-resistant surface these will adhere to the moulding compound. This adhesion will be greater in strength than the adhesion to the core, such that when the core is withdrawn the wear members will remain in the cast wear- resistant coating. To facilitate the withdrawal of the core, the adhesive between the wear members and the core may be of such a nature that the adhesion between the core and the wear members ceases or is reduced when the adhesive is heated or exposed to certain chemicals. A wear-resistant coating and wear members may in a similar way be cast on to the end caps, but the process in this case will be far simpler than for the housing as a counter-mould may be used that is completely flat. In situ tests have shown that the wear-resistant coating according to the present invention has a considerably longer life than conventionally applied coatings.

Claims: P a t e n t c l a i m s 1. A wear-resistant coating arrangement (6) in a rotating gate feeder (1) for feeding substantially particulate material, comprising a housing (2) and a rotor (3) and also end caps (8) at each end of the housing, characterised in that the wear- resistant coating (6) is cast directly on to the inner wall (14) of the housing which faces towards the rotor (3) , with the inner wall (14) of the housing functioning as an outer mould and with a purpose-adapted core (15) as an inner mould. 2. The arrangement according to Claim 1, characterised in that the housing (2) is designed to have one or more filler holes (7) for the moulding compound. 3. The arrangement according to Claims 1 - 2, characterised in that the housing (2) is provided with release zones at certain points on the surfaces (14) which face towards the cast wear- resistant coating (6) . 4. The arrangement according to Claims 1 - 3 , characterised in that the moulding compound in the surface (18) thereof facing towards the rotor (3) has one or more wear members (12) embedded therein having greater wear resistance than the moulding compound. 5. The arrangement according to Claims 1 - 4, characterised in that the surface of the core (15) forms a cyclindrical sector against the inner wall (14) of the housing with a radius of curvature which is equal to the outermost radial extent of the rotor (3) . 6. The arrangement according to Claim 5, characterised in that the core (15) consists of two core halves (15a, 15b) which are pressed against each half of the housing (2) . 7. The arrangement according to Claims 1 - 6, characterised in that the wear-resistant coating (6) consists of a proportion of granular and extremely hard particles, held togther by a binder, which form a rough surface having a high resistance coefficient against the through-flowing air or gas in the gap between the rough surface (18) and the blades of the rotor (3) . 8. A method for providing a wear-resistant coating (6) in a rotating gate feeder (1) for feeding substantially particulate material, comprising a housing (2) and a rotor (3) and also end caps (8) at each end of the housing, characterised in that the wear-resistant coating (6) is cast directly on to the inner wall of the housing (2) which faces towards the rotor (3) , with the housing (2) functioning as an outer mould and with a purpose-adapted core (15) functioning as an inner mould. 9. The method according to Claim 8, characterised in that the moulding compound is poured into the hollow space between the housing (2) and the core (15) through a hole (7) in the housing wall . 10. The method according to Claims 8 - 9, characterised in that a release coating is applied at certain points on the inner wall (14) of the housing which faces towards the rotor (3) , prior to the wear-resistant coating being cast in place. 11. The method according to Claims 8 - 10, characterised in that the core on the surface (19) thereof which comes to lie against the moulding compound is equipped with one or more wear members (12) which have greater adhesion against the moulding compound than against the core (15) , and which, after the hardening of the moulded compound, can be released from the core (15) so that they remain embedded in the moulding compound. 12. The method according to Claims 8 - 11, characterised in that the wear-resistant coating (6) is cast from a mixture of granular and extremely hard particles and a binder which, after casting, is allowed to form a rough surface (18) towards the rotor.

Inventors: LUND IVAR, LUND, IVAR
Applicants: FILTER OG STOEVTEKNIKK AS, LUND IVAR, FILTER- OG STOEVTEKNIKK A/S, LUND, IVAR
Application year: 1994
Main classification: B01J3
IPC codes: B01J8, B65G53